JPWO2015080103A1 - Purging agent and purging method using the same - Google Patents

Abstract

The purging agent of the present invention is used for purging a resin to be purged containing an ethylene-vinyl ester copolymer saponified resin, and contains at least one metal salt selected from the group consisting of alkali metal salts and alkaline earth metal salts. The hydrocarbon-based resin composition is contained in a relatively large amount, and the shear viscosity ratio obtained from the following formula satisfies a specific range. Shear viscosity ratio = η (X) / η (Y) [where η (X) is a shear viscosity (Pa · S) at a temperature of 230 ° C. and a shear rate of 12.2 sec−1, and η (Y) is a temperature. The shear viscosity (Pa · S) is 230 ° C. and the shear rate is 1824 sec−1. ]

Description

  The present invention relates to a purging agent used in an apparatus for melt-molding a thermoplastic resin, and more particularly to a purging agent suitable for an ethylene-vinyl ester copolymer saponified resin and a purging method using the same. It is.

  Conventionally, ethylene-vinyl ester copolymer saponified resin (hereinafter sometimes referred to as EVOH resin), polyvinyl alcohol resin (hereinafter sometimes referred to as PVA resin), polyamide resin (hereinafter referred to as PA resin). High-polarity thermoplastic resins, such as sometimes referred to, are excellent in gas barrier properties, and are generally used by being molded into packaging films or containers for foods, etc. by a melt molding method.

  However, when the thermoplastic resin is melt-molded for a long time, a part of the thermoplastic resin stays in the resin flow path of a melt-molding machine such as an extruder for a long time, causing gelation, thermal deterioration, decomposition, etc. As a result, there are problems that streaks are generated in the product, and gel is mixed into the product to cause a product defect.

  In this way, when streaks are generated or gel is mixed in the product, the manufacturing operation is stopped, and the thermoplastic resin that is stuck in the resin flow path of the melt molding machine using a purging agent is stuck. It is effective to wash and remove.

Conventionally, as such a purging agent, a purging agent using a hydrocarbon-based resin composition containing a relatively large amount of at least one metal salt selected from the group consisting of alkali metal salts and alkaline earth metal salts is known. (For example, refer to Patent Document 1).
This purging agent has an action of transferring a metal salt to the purged resin and decomposing the purged resin, thereby obtaining an excellent cleaning effect.

Japanese Unexamined Patent Publication No. 2012-31404

  However, the purging agent of Patent Document 1 has been found to have an insufficient cleaning effect in a severe environment with a narrow flow path and high temperature, such as a die portion of a melt molding machine.

  Accordingly, an object of the present invention is to provide a purging agent having a more excellent cleaning effect.

As a result of intensive studies in view of the above circumstances, the present inventor includes a hydrocarbon resin and at least one metal salt selected from the group consisting of an alkali metal salt and an alkaline earth metal salt. A purging agent in which the content of the metal salt is more than 1% by weight and not more than 20% by weight in terms of metal and the shear viscosity ratio obtained from the following formula is 12 to 16, particularly ethylene-vinyl ester-based co-agents. It has been noted that it is effective for purging a purged resin containing a polymer saponified resin.
Shear viscosity ratio = η (X) / η (Y)
[Here, eta (X) is a temperature 230 ° C., a shear viscosity of the shear rate ^{12.2sec -1 (Pa · S),} η (Y) is a temperature 230 ° C., the shear viscosity of the shear rate 1824sec ^-1 (Pa -S). ]

  That is, the present invention uses a hydrocarbon resin composition containing a relatively large amount of at least one metal salt selected from the group consisting of alkali metal salts and alkaline earth metal salts as a purging agent. A purging agent having a large shear viscosity ratio between a high shear rate and a low shear rate is used.

  When melt-molding a thermoplastic resin (resin to be purged) using a melt-molding machine such as an extruder, generally, the higher the shear viscosity at a low shear rate, the longer the residence in the resin flow path. It is considered that the purge performance for washing and removing the thermoplastic resin is good.

  However, surprisingly, by using a material having a large shear viscosity ratio due to a specific shear rate, an excellent cleaning effect can be obtained even in a severe environment where the flow path is narrow and the temperature is narrow like the die part of a melt molding machine. As a result, the present invention was completed.

  The purging agent of the present invention preferably has a melt flow rate of 0.2 to 20 g / 10 min at 230 ° C. and a load of 2160 g.

  The present invention also relates to a method for purging a purged resin existing in a melt molding machine using the above-described purging agent.

  Further, the present invention includes filling the above-mentioned purging agent, stopping the screw in a state where the melt molding machine is filled with the purging agent, and leaving it for 5 minutes to 5 hours, and discharging the purging agent. The present invention relates to a purging method for a resin to be purged existing in a melt molding machine.

  In the present invention, when a hydrocarbon-based resin composition containing a relatively large amount of at least one of alkali metal salts and alkaline earth metal salts is used as a purging agent, the purging agent has a specific range. By satisfying the shear viscosity ratio, the resin to be purged in the melt molding machine, particularly the purged resin including the saponified resin of ethylene-vinyl ester copolymer, is excellent in cleaning and removing effect, like the die part of the melt molding machine. In addition, an excellent cleaning effect is exhibited even in a severe environment with a narrow flow path and a high temperature.

  Hereinafter, although it demonstrates in detail about the structure of this invention, these show an example of a desirable embodiment and are not specified by these content.

  The purging agent of the present invention cleans the thermoplastic resin staying in the resin flow path in the melt molding machine when melt molding the thermoplastic resin (resin to be purged) using a melt molding machine such as an extruder. Used for removal.

  In the present invention, the barrel temperature of the extruder means the surface temperature of the barrel of the extruder. When the barrel of the extruder has a plurality of sections and each section is set to a different temperature, the highest temperature is set as the barrel temperature.

<Purging agent>
The purging agent of the present invention is a composition containing a relatively large amount of at least one metal salt selected from the group consisting of alkali metal salts and alkaline earth metal salts based on a hydrocarbon resin.
The content of the hydrocarbon resin in the purging agent composition of the present invention is usually 80% by weight or more, preferably 85% by weight or more.

[Hydrocarbon resin]
The hydrocarbon resin used as the base of the purging agent of the present invention is a polymer having a hydrocarbon monomer as a main monomer of usually 80 mol% or more and a molecular weight of usually 10,000 or more, and the main chain is composed of only carbon bonds. It is a polymer composed of
Such a hydrocarbon resin has a property that it is difficult to adhere to the metal constituting the melt molding machine because the polarity of the resin is low.
From the viewpoint of discharging properties of the purging agent, the content of the copolymerizable monomer other than the hydrocarbon-based monomer is preferably less than 20 mol%.

  Examples of the hydrocarbon resin include polyolefin resins mainly composed of aliphatic hydrocarbon monomers and polystyrene resins mainly composed of aromatic hydrocarbon monomers.

The polyolefin resin mainly composed of aliphatic hydrocarbon monomers will be described. Specific examples of the aliphatic hydrocarbon monomer include ethylene, propylene, and butene.
The polyolefin resin refers to a homopolymer composed of these aliphatic hydrocarbon monomers, a random copolymer of two or more olefin monomers, and a block copolymer.
For example, ultra-low density polyethylene, (linear) low density polyethylene, high density polyethylene, ethylene-propylene copolymer, ethylene-octene copolymer, ethylene-α olefin copolymer such as ethylene-hexene copolymer, Polypropylene resins such as polyethylene resins such as polypropylene, propylene-ethylene copolymers, propylene-α olefin copolymers such as propylene-butene copolymers; polybutenes, polymethylpentenes and the like.

  A polystyrene resin mainly composed of an aromatic hydrocarbon monomer will be described. Specific examples of the aromatic hydrocarbon monomer include styrene and methylstyrene. Examples of the polystyrene resin include homopolymers composed of these aromatic hydrocarbon monomers, random copolymers of two or more monomers, and block copolymers.

  From the viewpoint of the dischargeability and economic efficiency of the purging agent, the hydrocarbon resin is preferably a polyethylene resin or a polypropylene resin, particularly preferably a polyethylene resin, particularly preferably a low density polyethylene, and even a linear resin. Low density polyethylene.

In the present invention, a purging agent having a large shear viscosity ratio at a specific shear rate (sec ⁻¹ ) is used. However, in the hydrocarbon resin used as the base of the purging agent, a specific shear rate (sec ⁻ It is preferable to control the shear viscosity ratio in ¹ ).

The shear viscosity: η (x) of the above hydrocarbon-based resin at a temperature of 230 ° C. and a shear rate of 12.2 sec ⁻¹ is usually 1500 to 4500 Pa · S, preferably 2000 to 4000 Pa · S, particularly preferably 2500. ˜3500 Pa · S.

The above-mentioned hydrocarbon resin having a temperature of 230 ° C. and a shear rate of 1824 sec ⁻¹ has a shear viscosity η (y) of usually 80 to 350 Pa · S, preferably 120 to 300 Pa · S, particularly preferably 160 to 250 Pa. -S.

The shear viscosity ratio of such a hydrocarbon-based resin is obtained from the following formula, and is usually 13.0 to 17.0, preferably 13.5 to 16.5, and particularly preferably 14.0 to 14.0. 15.5 Pa · S.
Shear viscosity ratio = η (x) / η (y)
[Here, η (x) is the temperature 230 ° C., a shear viscosity of the shear rate ^{12.2sec -1 (Pa · S),} η (y) is a temperature 230 ° C., the shear viscosity of the shear rate 1824sec ^-1 (Pa -S). ]
The shear viscosity ratio of the hydrocarbon resin can be calculated from the results obtained by measuring the shear viscosity at 230 ° C. and each shear rate using a capillary rheometer (flow characteristic measuring device).

The density of the hydrocarbon resin is a value measured in accordance with the provisions of JIS K7112 (1999), is usually 0.85~0.98g / cm ^3, more 0.90~0.95g / cm ³ Preferably 0.91 to 0.94 g / cm ³ , more preferably 0.92 to 0.93 g / cm ³ . When this value is in the above range, the purging effect tends to be obtained more remarkably.

  Further, the melt flow rate (MFR) of the hydrocarbon-based resin is usually 0.1 to 50 g / 10 minutes, preferably 0.2 to 10 g / 10 minutes under a condition of 190 ° C. and a load of 2160 g, More preferably, it is 0.5-5 g / 10min. When this value is in the above range, the purging effect tends to be obtained more remarkably.

The number average molecular weight of the hydrocarbon-based resin is usually 1 × 10 ^{4 to} 5 × 10 ⁴ , and preferably 2 × 10 ⁴ to 4 × as measured by GPC (gel permeation chromatography) with polystyrene as a standard. 10 is ^4, more preferably 3 × ¹⁰ 4 to 3.8 × 10 ^4, particularly preferably 3 × ¹⁰ 4 to 3.5 × 10 ^4. When this value is in the above range, the purging effect tends to be obtained more remarkably.

  The molecular weight dispersity (weight average molecular weight / number average molecular weight) of the hydrocarbon resin is usually 3 to 6, preferably 3.2 to 5, particularly preferably 3.5 to 4.5. . When this value is in the above range, the purging effect tends to be obtained more remarkably.

[Metal salt]
The purging agent of the present invention is a composition based on a hydrocarbon resin and containing a relatively large amount of at least one metal salt selected from the group consisting of alkali metal salts and alkaline earth metal salts.
Accordingly, the content of the metal salt with respect to the hydrocarbon resin of the purging agent of the present invention is more than 1 wt% and not more than 20 wt%, particularly preferably 1.2 to 10 wt% in terms of metal. %, Particularly preferably 1.5 to 3% by weight. If the amount is too large, the productivity and economy tend to decrease, and if it is too small, the cleaning effect tends to be insufficient.

  The alkali metal and alkaline earth metal in at least one metal salt selected from the group consisting of the alkali metal salts and alkaline earth metal salts have a function of decomposing the purged resin. Specifically, examples of the alkali metal include lithium, sodium, potassium, rubidium, and cesium, and examples of the alkaline earth metal include beryllium, magnesium, calcium, strontium, and barium. Among these, alkaline earth metals are preferred, and magnesium and calcium are particularly preferred from the viewpoints of easy availability, economy, and purging performance.

  Examples of the metal salts of the alkali metal salt and alkaline earth metal salt include organic salts and inorganic salts. Such a salt is preferably a low molecular compound from the viewpoint of dispersibility in the resin composition.

The organic salt means a carboxylate, such as acetate, oxalate, laurate, myristate, palmitate, stearate, alginate, heptadecylate, behenate, olein Acid salts, elaidate salts, elicitate salts, linoleate salts, linolenate salts, ricinoleate salts, hydroxy stearates, montanates, isostearates, epoxy stearates and the like.
Among these, a long-chain aliphatic carboxylate having a relatively large number of carbon atoms is preferable from the viewpoint of having surface activity. Preferred is a carboxylate having 10 to 25 carbon atoms, more preferred is a carboxylate having 12 to 22 carbon atoms, and particularly preferred is a carboxylate having 14 to 20 carbon atoms. When the number of carbons is too large, generality tends to be lacking, and when the number of carbons is too small, purging performance tends to be insufficient due to insufficient surface activity during melting.
That is, the organic salt is preferably a Group 2 metal salt of a carboxylic acid having 14 to 20 carbon atoms, and most preferably a magnesium carboxylate having 14 to 20 carbon atoms.

  The melting point of such an organic salt is usually 100 to 220 ° C, preferably 110 to 180 ° C, particularly preferably 120 to 160 ° C. When the organic salt is melted in the flow path, it is preferable in that the surface activity is exhibited.

The said inorganic salt means the salt which has an anion derived from an inorganic compound, For example, borate, a phosphate, carbonate, a sulfate, etc. are mentioned. Among these, basic inorganic salts are preferable and carbonates are particularly preferable from the viewpoint that the effect of decomposing the EVOH resin is high and the cleaning effect is high.
In particular, magnesium carbonate is preferable because it is stable in the state of basic magnesium carbonate and is commercially available in this state.

  Since the inorganic salt does not melt in the resin flow path, it is considered that the inorganic salt has an effect of physically scavenging the purged resin stuck in the resin flow path.

  The particle diameter of the metal salt used for producing the purging agent of the present invention is preferably small in order to suppress moldability and retention in the apparatus. Preferably, in the particle size distribution measurement by the laser diffraction scattering method, the average particle size of the metal salt is usually 20 microns or less.

The metal salt used to produce the purging agent of the present invention is preferably a combination of the organic salt and the inorganic salt. In particular, the weight ratio of inorganic salt / organic salt is generally 0.05 to 10, preferably 0.1 to 8, particularly preferably 0.2 to 5, and particularly preferably 1 to 1.5.
The metal species of the inorganic salt and the organic salt may be the same or different. From the point of discharge of the purging agent, the same species is preferred.
And it is preferable to use carbonate as an inorganic salt and long-chain aliphatic carboxylate as an organic salt from the point of economical efficiency and productivity of a raw material, and a cleaning effect.
Most preferably, magnesium carbonate is used as the inorganic salt, and magnesium carboxylate having 14 to 20 carbon atoms is used as the organic salt.

  In the case where an inorganic salt and an organic salt are used in combination in such a metal salt, the cleaning effect due to decomposition of the purged resin by the metal salt is enhanced. Furthermore, since the inorganic salt has a melting point of usually 500 ° C. or higher and is much higher than the melt molding temperature of a general thermoplastic resin, it does not melt in the resin flow path and remains on the resin flow path wall. It is thought that it plays a role of scrubbing off by friction. And since organic salts, such as a higher fatty acid salt, are 1 type of surfactant, it is estimated that it has the effect which the to-be-purged resin adhering to the inside of a resin flow path floats from a metal surface, and peels off.

[Other ingredients]
In the purging agent of the present invention, the heat stabilizer such as hindered phenol or hindered amines, usually less than 3% by weight, preferably less than 1% by weight with respect to the total amount of the purging agent, silicon-based or Fluorine fatty acid ester, amide lubricant, foaming agent, filler (metal oxide, hydroxide, etc.) and the like may be contained.

[Shear viscosity ratio of purging agent]
The purging agent of the present invention is characterized in that the shear viscosity ratio obtained from the following formula is in a specific range.
Shear viscosity ratio = η (X) / η (Y)
[Here, eta (X) is a temperature 230 ° C., the shear viscosity of the shear rate ^{12.2sec -1 (Pa · S),} η (Y) is a temperature 230 ° C., the shear viscosity of the shear rate 1824sec ^-1 (Pa · S ). ]

  Such shear viscosity ratio is usually 12.0 to 16.0, preferably 12.5 to 15.0, particularly preferably 13.0 to 14.5. If the shear viscosity ratio is too low, the effect of cleaning and removing the resin to be purged tends to be insufficient, while if too high, the purging agent itself tends to be difficult to be discharged. The shear viscosity ratio of the purging agent can be calculated from the results obtained by measuring the shear viscosity at 230 ° C. and each shear rate using a capillary rheometer (flow characteristic measuring device).

Shear viscosity: η (X) of the purging agent at a temperature of 230 ° C. and a shear rate of 12.2 sec ⁻¹ is usually 1000 to 4000 Pa · S, preferably 1500 to 3500 Pa · S, and particularly preferably 2000 to 3000 Pa. -S.

The purging agent having a temperature of 230 ° C. and a shear rate of 1824 sec ⁻¹ has a shear viscosity: η (Y) of usually 60 to 340 Pa · S, preferably 100 to 280 Pa · S, particularly preferably 130 to 240 Pa · S. It is.

  The melt flow rate (MFR) of the purging agent of the present invention is preferably 0.2 to 20 g / 10 min at 230 ° C. and a load of 2160 g, more preferably 0.5 to 15 g / 10 min, and particularly Preferably it is 1-10 g / 10min. When this value is too large, the purging effect tends not to be sufficiently exhibited.

<Method for producing purging agent>
The purging agent of the present invention is prepared by compounding the above-described metal salt and a base hydrocarbon resin.
A known method can be used for such a compound. Of these, the use of an extruder is preferable from the viewpoint of processability and economy. The type of the extruder is not particularly limited, and a general extruder such as a single-screw extruder, a twin-screw extruder, or a multi-screw extruder can be employed.
The barrel temperature of the extruder when compounding with the extruder is usually 150 to 300 ° C, preferably 160 to 280 ° C, particularly preferably 170 to 250 ° C.

  And it is preferable that the metal salt in this purging agent is disperse | distributing uniformly in the hydrocarbon resin used as a base.

  The purging agent of the present invention is preferably formed into pellets after compounding as described above. A known method can be adopted as a method of forming pellets. Such pellets usually have a spherical shape, a cylindrical shape, a cubic shape, a rectangular parallelepiped shape, etc., and a cylindrical pellet is preferable, and the diameter is usually 1 to 5 mm and the length is usually 1 to 5 mm.

<Purged resin>
The thermoplastic resin (that is, the purged resin) that is the object of the purging agent of the present invention includes an ethylene-vinyl ester copolymer saponified resin (EVOH resin). EVOH resin is a high-polarity thermoplastic resin that has a characteristic that it easily adheres to the metal of a melt molding machine and is difficult to remove. Polar group-containing thermoplastic resins are often used as an intermediate layer for packaging materials such as foods because of their gas barrier performance. Among them, EVOH resins are widely used because of their excellent gas barrier properties and good safety. The purging agent of the present invention can be effectively used for purging of the purged resin containing such EVOH resin.

[EVOH resin]
The EVOH resin used in the present invention is usually a resin obtained by copolymerization of ethylene and a vinyl ester monomer and then saponification, and is a water-insoluble thermoplastic resin. As the polymerization method, any known polymerization method such as solution polymerization, suspension polymerization, and emulsion polymerization can be used. In general, solution polymerization using methanol as a solvent is used. Saponification of the obtained ethylene-vinyl ester copolymer can also be performed by a known method.
That is, the EVOH resin mainly contains a vinyl alcohol structural unit and a vinyl alcohol structural unit, and contains a slight amount of vinyl ester structural unit remaining without being saponified.

  As the vinyl ester monomer, vinyl acetate is typically used from the viewpoint of market availability and good impurity treatment efficiency during production. In addition, for example, aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, benzoic acid, etc. Examples thereof include aromatic vinyl esters such as vinyl, and are usually aliphatic vinyl esters having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms. These are usually used alone, but a plurality of them may be used simultaneously as necessary.

  The content of the ethylene structural unit in the EVOH resin is a value measured based on ISO 14663, and is usually 20 to 60 mol%, preferably 25 to 50 mol%, particularly preferably 25 to 35 mol%. If the content is too low, gas barrier properties and melt moldability under high humidity conditions tend to be reduced, and conversely if too high, gas barrier properties tend to be insufficient.

  The saponification degree of the vinyl ester component in the EVOH resin is a value measured based on JIS K6726 (however, the EVOH resin is a solution uniformly dissolved in water / methanol solvent), and is usually 90 to 100 mol%, preferably 95. -100 mol%, particularly preferably 99-99.9 mol%. When the degree of saponification is too low, gas barrier properties, thermal stability, moisture resistance and the like tend to decrease.

  Further, the melt flow rate (MFR) (210 ° C., load 2,160 g) of the EVOH resin measured using a melt indexer (extrusion plastometer) is usually 0.5 to 100 g / 10 minutes, preferably Is 1 to 50 g / 10 min, particularly preferably 3 to 35 g / 10 min. When the MFR is too large, the film forming property tends to be unstable, and when it is too small, the viscosity becomes too high and melt extrusion tends to be difficult.

Further, the EVOH resin in the present invention may further contain structural units derived from the comonomer shown below within a range not inhibiting the effects of the present invention (for example, 10 mol% or less).
The comonomer includes olefins such as propylene, 1-butene and isobutene, 3-buten-1-ol, 3-butene-1,2-diol, 4-penten-1-ol, 5-hexene-1,2- Hydroxyl group-containing α-olefins such as diols, derivatives thereof such as esterified products and acylated products, acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, etc. Saturated acids or salts thereof, mono- or dialkyl esters having 1 to 18 carbon atoms, acrylamide, N-alkyl acrylamides having 1 to 18 carbon atoms, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or salts thereof, acrylamidopropyl Acrylic acid such as dimethylamine or its acid salt or its quaternary salt Methacrylamide, N-alkylmethacrylamide having 1 to 18 carbon atoms, N, N-dimethylmethacrylamide, 2-methacrylamideamidesulfonic acid or its salt, methacrylamidepropyldimethylamine or its acid salt or its quaternary Methacrylamides such as salts, N-vinyl amides such as N-vinyl pyrrolidone, N-vinyl formamide, N-vinyl acetamide, vinyl cyanides such as acrylonitrile and methacrylonitrile, alkyl vinyl ethers having 1 to 18 carbon atoms, hydroxy Vinyl ethers such as alkyl vinyl ethers and alkoxyalkyl vinyl ethers, vinyl chlorides, vinylidene chloride, vinyl halides such as vinyl fluoride, vinylidene fluoride and vinyl bromide, vinyls such as trimethoxyvinyl silane Allyl halide compounds such as silane, allyl acetate, allyl chloride, allyl alcohol such as allyl alcohol, dimethoxyallyl alcohol, trimethyl- (3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropane And comonomers such as sulfonic acid.

  Furthermore, “post-modified” EVOH-based resins such as urethanization, acetalization, cyanoethylation, oxyalkyleneation, and the like can also be used.

In particular, an EVOH resin obtained by copolymerizing a hydroxy group-containing α-olefin is preferable in terms of good secondary moldability, and among them, an EVOH resin having a 1,2-diol in the side chain is preferable.
Such EVOH resin having 1,2-diol in the side chain contains 1,2-diol structural units in the side chain. The 1,2-diol structural unit is specifically a structural unit represented by the following structural unit (1).

[In General Formula (1), R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic group, X represents a single bond or a bonded chain, and R ⁴ , R ⁵ , and R ⁶ represent Each independently represents a hydrogen atom or an organic group. ]

The organic group in the 1,2-diol structural unit represented by the general formula (1) is not particularly limited, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. And saturated hydrocarbon groups such as tert-butyl group, aromatic hydrocarbon groups such as phenyl group and benzyl group, halogen atom, hydroxyl group, acyloxy group, alkoxycarbonyl group, carboxyl group and sulfonic acid group.
R ^{1 to} R ³ are usually a saturated hydrocarbon group or a hydrogen atom having 1 to 30 carbon atoms, particularly 1 to 15 carbon atoms, more preferably 1 to 4 carbon atoms, and most preferably a hydrogen atom. R ^{4 to} R ⁶ are preferably an alkyl group having 1 to 30 carbon atoms, particularly 1 to 15 carbon atoms, more preferably 1 to 4 carbon atoms, or a hydrogen atom, and most preferably a hydrogen atom. In particular, it is most preferable that R ^{1 to} R ⁶ are all hydrogen.

Moreover, X in the structural unit represented by the general formula (1) is typically a single bond.
In addition, a bond chain may be used as long as the effect of the present invention is not inhibited. The bonding chain is not particularly limited, but is a hydrocarbon chain such as alkylene, alkenylene, alkynylene, phenylene, naphthylene or the like (these hydrocarbons may be substituted with a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom). ) _{other, -O -, - (CH 2} O) m -, - (OCH 2) m -, - (CH 2 O) m CH 2 - structure containing an ether binding site, such as, -CO -, - COCO _{-, - CO (CH 2)} m CO -, - CO (C 6 H 4) CO- structure containing a carbonyl group such as, -S -, - CS -, - SO -, - SO 2 - , etc. sulfur atoms structure containing, -NR -, - CONR -, - NRCO -, - CSNR -, - NRCS -, - structure containing a nitrogen atom such as NRNR-, -HPO ₄ - heteroatoms such structure containing a phosphorus atom, such as A structure containing- _{i (OR) 2 -, -} OSi (OR) 2 -, - OSi (OR) structure containing 2 O- such as silicon _{atoms, -Ti (OR) 2 -,} - OTi (OR) 2 -, - OTi ( OR) ₂ O— and other structures including titanium atoms, —Al (OR) —, —OAl (OR) —, structures including aluminum atoms such as —OAl (OR) O—, and the like. Can be mentioned. In addition, R is an arbitrary substituent each independently, a hydrogen atom and an alkyl group are preferable, and m is a natural number, and is 1-30 normally, Preferably it is 1-15, More preferably, it is 1-10. Among them, —CH ₂ OCH ₂ — and a hydrocarbon chain having 1 to 10 carbon atoms are preferable from the viewpoint of stability at the time of production or use, and further, a hydrocarbon chain having 1 to 6 carbon atoms, particularly 1 carbon atom. It is preferable that

The most preferable structure in the 1,2-diol structural unit represented by the general formula (1) is one in which R ^{1 to} R ⁶ are all hydrogen atoms and X is a single bond. That is, the structural unit represented by the following structural formula (1a) is most preferable.

  In particular, when the 1,2-diol structural unit represented by the general formula (1) is contained, the content thereof is usually 0.1 to 20 mol%, further 0.1 to 15 mol%, and particularly preferably 0.1. The thing of 1-10 mol% is preferable.

  In addition, the EVOH resin used in the present invention may be a mixture with other different EVOH resins. Examples of such other EVOH resins include 1,2-diol structural units represented by the general formula (1). Examples include those having different contents, those having different ethylene contents, those having different saponification degrees, those having different polymerization degrees, those having different MFRs, and those having different other copolymerization components.

  In the EVOH resin used in the present invention, a compounding agent generally blended with the EVOH resin, for example, a heat stabilizer, an antioxidant, an antistatic agent, a colorant, an ultraviolet absorber, within a range not inhibiting the effects of the present invention. Lubricant, plasticizer, light stabilizer, surfactant, antibacterial agent, drying agent, antiblocking agent, flame retardant, crosslinking agent, curing agent, foaming agent, crystal nucleating agent, antifogging agent, biodegradation additive, silane A coupling agent, an oxygen absorbent, etc. may be contained.

  The heat stabilizer is an organic acid such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, behenic acid, or an alkali thereof for the purpose of improving various physical properties such as heat stability during melt molding. Metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), salts such as zinc salts; or inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, phosphoric acid, boric acid, or alkali metals thereof Additives such as salts such as salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc salts, etc. may be added in small amounts in advance.

  In the purged resin, the EVOH resin content is preferably 1% by weight or more, and 1 to 99% by weight of the purged resin is allowed. The purged resin may be composed of only EVOH resin.

  Since polar group-containing thermoplastic resins tend to lower gas barrier properties due to moisture, they are usually bonded as a surface layer with a hydrophobic thermoplastic resin (eg, polyolefin resin, polystyrene resin, polyester resin, etc.) and sometimes between each layer. Used as a packaging material or the like as a multilayer structure having a functional resin (for example, an unsaturated carboxylic acid-modified polyolefin resin).

When manufacturing the multilayer structure, scraps generated in the manufacturing process are often recovered, and the recovered material is melt-molded again by an extruder and recycled as at least one layer of a new multilayer structure.
Such a recycling operation involves melting and mixing a resin composition containing a polar group-containing thermoplastic resin, a hydrophobic thermoplastic resin or an adhesive resin constituting the multilayer structure in an extruder, and the present invention. This purging agent is also effective when used for purging, that is, washing and removing, a resin composition containing such a highly polar resin from an extruder.

As described above, the purging agent of the present invention can be optimally used for purging the EVOH resin in the melt molding machine, but can also be used in the same manner for known thermoplastic resins. Examples of such thermoplastic resins include thermoplastic resins having a melting point (or a flow start temperature in the case of an amorphous resin) of usually 100 to 270 ° C, preferably 120 to 250 ° C, and particularly preferably 150 to 230 ° C. Examples of such thermoplastic resins include vinyl alcohol resins (PVA resins, etc.) other than EVOH resins, PA resins, polyolefin resins (linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene). , Ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene-acrylic acid ester copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polybutene , Polypentene, etc.), modified polyolefin resins obtained by graft-modifying unsaturated carboxylic acids to polyolefin resins, polyester resins, polyvinyl chloride resins, thermoplastic polyurethane resins, polyvinylidene chloride, acrylic resins, polystyrene resins, Vinyl ester Examples thereof include resins, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, chlorinated polypropylene, aromatic or aliphatic polyketones, and these may be used alone or in combination.
In particular, as described above, vinyl alcohol resins such as PVA resin, which is a high-polarity thermoplastic resin, and PA resins can be effectively cleaned in the same manner as EVOH resins.

  The purging agent of the present invention contains a relatively large amount of metal salt, and when applied to a vinyl alcohol resin such as EVOH resin or PVA resin, the metal salt migrates into the vinyl alcohol resin polymer, and the resin In particular, it is effective for cleaning vinyl alcohol resin, particularly EVOH resin, adhering to a narrow and high temperature portion such as a melt molding machine die.

  The resin to be purged of the present invention may contain a known general lubricant, metal oxide (for example, silicon oxide, titanium oxide used as a pigment), antioxidant, desiccant, filler, oxygen absorber.

<Target melt molding machine>
The melt molding machine used at the time of melt molding of the resin to be purged is not particularly limited, and a general extruder can be used. For example, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, etc. can be raised, but any of them may be used. In detail, single layer cast extruder, single layer inflation extruder, single layer blow extruder, injection molding machine, multilayer cast extruder, multilayer inflation extruder, multilayer blow extruder, co-injection molding machine etc. are also used .

<Purging method>
The purging agent of the present invention contains a relatively large amount of at least one metal salt selected from the group consisting of alkali metal salts and alkaline earth metal salts, so that the metal salt in the purging agent is contained in the purged resin. Since this metal salt decomposes the resin to be purged, the purge performance is excellent even in the die portion of a melt molding machine having a narrow flow path and a severe environment with high temperature, and the cleaning effect is excellent.

  Furthermore, a publicly known method can be adopted as a purging method using the purging agent of the present invention. Specifically, after the thermoplastic resin is melt-molded by a melt molding machine, the purging agent of the present invention is supplied, filled in the melt molding machine, and then discharged.

  The temperature of the melt molding machine at the time of melt molding of the thermoplastic resin (resin to be purged) (for example, the barrel temperature of the extruder in the extruder) is usually 150 to 260 ° C.

The temperature of the melt molding machine (in the extruder, the barrel temperature of the extruder) when filling the inside of the melt molding machine with the purging agent of the present invention is usually 180 to 280 ° C, preferably 200 to 260 ° C. Preferably it is 210-260 degreeC, Most preferably, it is 230-260 degreeC. When the temperature is too high, the viscosity of the purging agent tends to decrease, and the cleaning effect of the purged resin tends to decrease. When the temperature is too low, the discharge performance of the purging agent itself tends to decrease.
Here, the temperature of the melt molding machine at the time of melt molding of the thermoplastic resin or filling with the purging agent means, for example, in the extruder, the barrel temperature of the extruder, that is, the surface temperature of the barrel of the extruder. When the barrel of the extruder has a plurality of sections and each section is set to a different temperature, the highest temperature is set as the barrel temperature.

  The amount of the purging agent of the present invention is usually determined based on the size of the melt molding machine and the degree of contamination of the purged resin. 5 to 100 times, preferably 8 to 50 times, particularly preferably 10 to 30 times the volume that can be filled with the resin excluding the screw volume from the volume.

In the purging method of the present invention, after the purging agent is supplied and filled in a melt molding machine such as an extruder so that the metal salt in the purging agent easily moves into the purged resin, the inside of the melt molding machine is filled with the purging agent. It is preferable to stop the screw in a full state and leave it for a certain period of time. The standing time is usually 5 minutes to 5 hours, more preferably 0.2 to 3 hours, and particularly preferably 0.5 to 2 hours. If the time is too long, the cleaning effect tends to decrease due to a decrease in productivity or the deterioration of the purging agent itself, and if too short, the purging effect tends to decrease.
After the purging agent is filled in the extruder, the screw is stopped and left for a certain period of time, and then the purging agent is filled again and left for a certain period of time. When repeating the supplying step, it is preferable that the sum of the residence times of the purging agent in the melt molding machine is within the above range.

  Moreover, when using an extruder, the screw rotation speed of the extruder at the time of purging may be the same as that at the time of molding the resin to be purged from the viewpoint of convenience. From the point of practical use, it is usually 5 to 300 rpm, preferably 10 to 250 rpm, and particularly preferably 10 to 100 rpm. Note that it is expected that the extrusion effect of the purged resin is improved by periodically increasing and decreasing the screw rotation speed during purging.

  As described above, the purging agent of the present invention and the purging method using the same contain a relatively large amount of metal salt and a large shear viscosity ratio due to a specific shear rate. The excellent effect that an excellent cleaning effect can be obtained even in a die portion of a melt molding machine, which is a difficult environment, is exhibited.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the description of the examples unless it exceeds the gist.
In the examples, “part” means a weight basis unless otherwise specified.

<Example 1>

As a purging agent, linear low density polyethylene (“GS650” manufactured by NUC Corporation, MFR 0.6 g / 10 min (190 ° C., load 2160 g), density 0.92 g / cm ³ , temperature 230 ° C., shear rate 12.2 sec. ⁻¹ shear viscosity (Pa · S) = 2980, temperature 230 ° C./shear rate 1824 sec ⁻¹ shear viscosity (Pa · S) = 201, shear viscosity ratio (temperature 230 ° C./shear rate 12.2 sec ⁻¹ shear 90 parts of viscosity (Pa · S) / temperature 230 ° C., shear rate (Pa · S) of shear rate 1824 sec ⁻¹ ) = 14.8), and magnesium stearate (manufactured by Sakai Chemical Industry Co., Ltd., SM) -PG) and 5 parts of basic magnesium carbonate (manufactured by Kyowa Chemical Industry Co., Ltd., light) were dry blended.
In addition, the content of the metal salt in the purging agent is 10% by weight, the content of the metal salt with respect to the hydrocarbon resin is 1.5% by weight in terms of metal, and the temperature of the purging agent is 230%. shear viscosity ° C. · shear rate 12.2sec ^-1 (Pa · S) is 2360, a shear viscosity (Pa · S) 175 of the temperature 230 ° C. · shear rate 1824Sec ^-1, shear viscosity ratio (temperature 230 ° C. · shear shear viscosity speed 12.2sec ^-1 (Pa · S) / shear viscosity of temperature 230 ° C. · shear rate 1824sec ^-1 (Pa · S)) was 13.5. The shear viscosity ratio was calculated from the results obtained by measuring the shear viscosity at 230 ° C. and each shear rate with a capillary rheometer “Capillograph 1D” manufactured by Toyo Seiki Co., Ltd.
The dry blend was melt kneaded and pelletized using a twin screw extruder under the following conditions.
Screw diameter: 30mmφ
Extruder temperature: C2 / C3 / C4 / C5 / C6 ... C16 / D = 80/120/180/210/220 ... 220/230 ° C
Discharge rate: 25kg / h
Rotation speed: 250rpm
The MFR of the obtained pellet was 1.3 g / 10 min under the conditions of 230 ° C. and a load of 2160 g.

<Experiment model for reproducing the heat degradation state of purged resin>
Using the following single-screw extruder, the extruder and die temperature were set as follows, and an ethylene-vinyl acetate copolymer saponified product (ethylene content 29 mol%, saponification degree 99.8 mol%, MFR 3 4 g / 10 min (210 ° C., load 2160 g)) was discharged while being supplied for 30 minutes, and the product was allowed to stand for 2 hours while being heated to reproduce the state after long-term production of the EVOH resin molded product.
Screw type: Full flight Screw diameter: 40mmφ
L / D: 28
Screw compression ratio: 2.5
Die: Coat hanger die Extruder temperature: C1 / C2 / C3 / C4 / H / D = 220/250/260/260/260/240 ° C.
Rotation speed: 40rpm

<Purging operation>
Thereafter, the purging agent was supplied for 20 minutes while maintaining the extruder temperature. At this time, the screw speed was 20 rpm for the first 10 minutes and 40 rpm for the next 10 minutes. Then, the above-described purging agent was filled in the extruder at the above-mentioned extruder temperature and left for 1 hour.

[Purging effect]
Then, EVOH resin was again supplied to the extruder, and film formation was started. After film formation was performed for 2 hours, the purging agent in the extruder was replaced with a small amount of polyethylene, and then the extruder was disassembled. The state of dirt on the die was observed and evaluated according to the following evaluation criteria.
A: There was no deposit of the resin to be purged on the die.
○: A thin film is present on the die and a slight amount of deposits are present, but the viscosity of the deposits is sufficiently reduced and cleaning is easy.
Δ: A slightly thicker resin layer is attached to the die, and it takes more time to clean than the state of ○.
X: A thick resin layer is adhered to the die, and the viscosity of the deposit is not lowered so much, so that it takes more time for cleaning than the state of Δ.

<Example 2>
In Example 1, as a hydrocarbon-based resin, linear low density polyethylene (“NUCG7641” manufactured by NUC Corporation, MFR 0.6 g / 10 min (190 ° C., load 2160 g), density 0.922 g / cm ³ , temperature 230 ° C. · shear viscosity shear rate of ^{12.2sec -1 (Pa · S) =} 2710, shear viscosity (Pa · S) of the temperature 230 ° C. · shear rate 1824sec ^-1 = 192, the shear viscosity ratio (temperature 230 ° C. · shear rate Purging as in Example ¹ , except that 12.2 sec ⁻¹ shear viscosity (Pa · S) / temperature 230 ° C., shear rate 1824 sec ⁻¹ shear viscosity (Pa · S)) = 14.1) was used. Agents were prepared and evaluated in the same manner.
Incidentally, the shear viscosity of the temperature 230 ° C. · shear rate 12.2Sec ^-1 purging agent (Pa · S) is 2390, the shear viscosity of the temperature 230 ° C. · shear rate 1824sec ^-1 (Pa · S) is 171, shear viscosity ratio (shear viscosity shear viscosity temperature 230 ° C. · shear rate 12.2sec ^-1 (Pa · S) / temperature 230 ° C. · shear rate 1824sec ^-1 (Pa · S)) was 14.0.

<Comparative Example 1>
In Example 1, as a hydrocarbon-based resin, linear low density polyethylene (“Novatech LLUF230” manufactured by Nippon Polyethylene Co., Ltd., MFR 1.0 g / 10 min (190 ° C., load 2160 g), density 0.921 g / cm ³ , shear viscosity of the temperature 230 ° C. · shear rate ^{12.2sec -1 (Pa · S) =} 3490, shear viscosity (Pa · S) = 274 temperature 230 ° C. · shear rate 1824sec ^-1, shear viscosity ratio (temperature 230 ° C. · Example ¹ except that the shear viscosity (Pa · S) at a shear rate of 12.2 sec ⁻¹ / temperature 230 ° C., the shear viscosity at a shear rate of 1824 sec ⁻¹ (Pa · S)) = 12.8) was used. A purging agent was prepared and evaluated in the same manner.
Incidentally, the shear viscosity of the temperature 230 ° C. · shear rate 12.2Sec ^-1 purging agent (Pa · S) is 2620, the shear viscosity of the temperature 230 ° C. · shear rate 1824sec ^-1 (Pa · S) is 238, shear The viscosity ratio (shear viscosity at a temperature of 230 ° C. and shear rate of 12.2 sec ⁻¹ (Pa · S) / shear viscosity at a temperature of 230 ° C. and shear rate of 1824 sec ⁻¹ (Pa · S)) was 11.0.

<Comparative example 2>
In Example 1, as a hydrocarbon resin, metallocene linear low density polyethylene (“Prime Polymer Co., Ltd.“ SP1510 ”, MFR 1.0 g / 10 min (190 ° C., load 2160 g), density 0.913 g / cm ³ , shear viscosity of the temperature 230 ° C. · shear rate ^{12.2sec -1 (Pa · S) =} 3470, shear viscosity (Pa · S) = 312 temperature 230 ° C. · shear rate 1824sec ^-1, shear viscosity ratio (temperature 230 ° C. · except using shear viscosity (Pa · S) / shear viscosity of temperature 230 ° C. · shear rate 1824Sec ^-1 of shear rate 12.2Sec ^-1 a (Pa · S)) = 11.1 ), as in example 1 A purging agent was prepared and evaluated in the same manner.
Incidentally, the shear viscosity of the temperature 230 ° C. · shear rate 12.2Sec ^-1 purging agent (Pa · S) is 2840, the shear viscosity of the temperature 230 ° C. · shear rate 1824sec ^-1 (Pa · S) is 261, shear viscosity ratio (shear viscosity shear viscosity temperature 230 ° C. · shear rate 12.2sec ^-1 (Pa · S) / temperature 230 ° C. · shear rate 1824sec ^-1 (Pa · S)) was 10.9.

<Comparative Example 3>
In Example 1, as a hydrocarbon resin, metallocene linear low density polyethylene (“Prime Polymer Co., Ltd.“ SP2510 ”, MFR 1.5 g / 10 min (190 ° C., load 2160 g), density 0.923 g / cm ³ , shear viscosity (Pa · S) = 2250, the shear viscosity of the temperature 230 ° C. · shear rate ^{1824sec -1 (Pa · S) =} 264 temperature 230 ° C. · shear rate 12.2sec ^-1, shear viscosity ratio (temperature 230 ° C. · Example ¹ except that the shear viscosity (Pa · S) at a shear rate of 12.2 sec ⁻¹ / temperature 230 ° C., the shear viscosity at a shear rate of 1824 sec ⁻¹ (Pa · S)) = 8.5) was used. A purging agent was prepared and evaluated in the same manner.
In addition, the shear viscosity (Pa · S) of the purging agent at a temperature of 230 ° C. and a shear rate of 12.2 sec ⁻¹ is 2480, and the shear viscosity (Pa · S) at a temperature of 230 ° C. and a shear rate of 1824 sec ⁻¹ is 220. viscosity ratio (shear viscosity shear viscosity temperature 230 ° C. · shear rate 12.2sec ^-1 (Pa · S) / temperature 230 ° C. · shear rate 1824sec ^-1 (Pa · S)) was 11.3.

<Comparative example 4>
In Example 1, as a hydrocarbon-based resin, a metallocene linear low-density polyethylene (“Sumikasen E FV104” manufactured by Sumitomo Chemical Co., Ltd., MFR 1.0 g / 10 min (190 ° C., load 2160 g), density 0.913 g / cm ³ , temperature 230 ° C./shear rate 12.2 sec ⁻¹ shear viscosity (Pa · S) = 3920, temperature 230 ° C./shear rate 1824 sec ⁻¹ shear viscosity (Pa · S) = 332, shear viscosity ratio (temperature except for using the shear viscosity of 230 ° C. · shear rate 12.2sec ^-1 (Pa · S) / shear viscosity of temperature 230 ° C. · shear rate ^{1824sec -1 (Pa · S))} = 11.8), example A purging agent was prepared in the same manner as in No. 1 and evaluated in the same manner.
Incidentally, the shear viscosity of the temperature 230 ° C. · shear rate 12.2Sec ^-1 purging agent (Pa · S) 3310, the shear viscosity of the temperature 230 ° C. · shear rate 1824sec ^-1 (Pa · S) is 283, shear The viscosity ratio (shear viscosity at a temperature of 230 ° C. and shear rate of 12.2 sec ⁻¹ (Pa · S) / shear viscosity at a temperature of 230 ° C. and shear rate of 1824 sec ⁻¹ (Pa · S)) was 11.7.

<Reference Example 1>
The purging effect was similarly evaluated using the purging agent produced in Example 1 and using linear low density polyethylene (“GS650” manufactured by NUC Co., Ltd.) as the purged resin.

<Reference Example 2>
Using the purging agent prepared in Comparative Example 3 and using a linear low density polyethylene (“SP2510” manufactured by Prime Polymer Co., Ltd.) as the purged resin, the purging effect was similarly evaluated.

  Table 1 shows the results of Examples 1 and 2, Comparative Examples 1 to 4, and Reference Examples 1 and 2.

As can be seen from Table 1, it was found that Examples 1 and 2 using a purging agent having a large shear viscosity ratio at a specific shear rate had better purging effects than Comparative Examples 1 to 4.
Further, as can be seen from Example 1, Comparative Example 3 and Reference Examples 1 and 2, the purging agent produced in Comparative Example 3 exhibited a purging effect on polyethylene resin (Reference Example 2), but EVOH. It was found that the purging agent of the present invention can effectively obtain the purging effect for the EVOH resin, whereas the effect was not obtained for the resin.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on November 26, 2013 (Japanese Patent Application No. 2013-243495) and a Japanese patent application filed on November 12, 2014 (Japanese Patent Application No. 2014-229819). Incorporated herein by reference.

  The purging agent having a specific shear viscosity ratio of the present invention is very useful industrially because it has a good purging effect and particularly an excellent purging effect for EVOH resins widely used as packaging materials.

Claims (4)

A purging agent used for purging a purged resin containing an ethylene-vinyl ester copolymer saponified resin,
A hydrocarbon resin and at least one metal salt selected from the group consisting of an alkali metal salt and an alkaline earth metal salt, and the content of the metal salt relative to the hydrocarbon resin is 1 in terms of metal. A purging agent that exceeds 20% by weight and is 20% by weight or less, and the shear viscosity ratio determined by the following formula is 12-16.
Shear viscosity ratio = η (X) / η (Y)
[Here, eta (X) is a temperature 230 ° C., a shear viscosity of the shear rate ^{12.2sec -1 (Pa · S),} η (Y) is a temperature 230 ° C., the shear viscosity of the shear rate 1824sec ^-1 (Pa -S). ]   The purging agent according to claim 1, wherein the melt flow rate at 230 ° C and a load of 2160 g is 0.2 to 20 g / 10 min.   A method for purging a resin to be purged that exists in a melt molding machine using the purging agent according to claim 1.   Filling the melt molding machine with the purging agent according to claim 1, stopping the screw in a state where the interior of the melt molding machine is filled with the purging agent, and allowing to stand for 5 minutes to 5 hours, and the purging agent A method of purging a purged resin present in a melt molding machine, comprising discharging